Zimmer is overused and mainly coasts by these days, the last score he did that felt "fun" was the Pirates of the Caribbean trilogy.
Also this news was already known no? It's talked about in the making of MGS2 video that was released around the time of the game.
Also LOL at people posting examples of music from MGS2 saying it's better when it was Norihiko Hibino composing the gameplay and menu stuff. HGW only scored the cutscenes.